Figure 13a. Talc embolism in a 37-year-old male drug abuser. (a) Thin-section (1.5-mm collimation) CT scan obtained at the level of the left interlobar artery shows diffuse pulmonary involvement with ill-defined centrilobular small nodules (arrows). Note also the nodular branching structures (tree-in-bud appearance). (b) Photomicrograph (original magnification, x40; H-E stain) of the pathologic specimen shows necrotizing vasculitis at the center of the secondary pulmonary lobule (arrow).